2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199155We have developed a macroscopic description of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays due to the presence of the geo-magnetic field. This description offers a simple and direct insight in the relation between the properties of the air shower and the time-structure of the radio pulse.10 pages, 8 figures; submitted to Astroparticle PhysicsAstrophysicstext